THIOAMIDE-BASED SENSOR FOR ANIONS OF ENVIRONMENTAL AND BIOMEDICAL RELEVANCE Selective binding of anions occurs in numerous physiological and enzymatic processes in life and is of paramount importance for many applications such as potential prototypes of new sensory devices, new extraction agents, and biological carriers. Surprisingly, synthetic receptors and sensors for anions are still very limited. The proposal will focus on developing new anion receptors, binders and sensors, which will have application in improving human health and the environment. The project is based on the hypothesis that the introduction of (C=S)NH, as a binding site to a synthetic receptor, enhances anion binding ability, and a fluorophore group if linked to the molecule displays a detectable optical change in presence of an anion. The long term goal of this project is to provide strategies for the design of highly selective sensor systems, and thus it will add a new dimension to the field of anion sensor chemistry. In Specific Aim 1, a new series of thioamide-based receptors with different spacers and variable rigidity will be synthesized, which include (1) acyclic thioamide receptors with TREN, aromatic and crown ether units, (ii) macrocyclic thioamide receptors with variable spacers, and (iii) optical sensors containing pyrene and dansyl groups. Series (i) and (ii) will bind anions through (C=S)NH...X- interactions, while the signaling unit(s) in series (iii) will serve as anion sensing. Specific Aim 2 is designed to investigate the binding properties of the synthesized molecules for anions in different solvents. The target anions are sulfate, phosphate, nitrate, perchlorate and halides, which are directly related to environment health and public health. Specific Aim 3 will focus on isolating complexes of anions bound to our synthetic ligands, and determining the structure of those complexes by X-ray crystallography. In Specific Aim 4, the cytotoxicity of thioamide-based ligands will be studied in both human liver carcinoma and human thyroid cancer cells using the MTT assay. Successful completion of this project will contribute greatly to the development of a framework for environmental and biomedical applications, and to the achievement the overall goals of RCMI at Jackson State University.